New figures compiled by tax experts reveal a plan tabled by senior Government officials - at a cost of €300m - to cut the main rate by almost 1pc would leave a single employee with a €38,000 wage just €3.34 a week, or €174 a year, better off.

This is the same as a 0.9pc pay rise, which is less than half the average wage increase being brokered by unions for workers across the country.

A married couple with one income of €50,000 would benefit to the tune of only €5 a week under the proposal to cut the main 5.5pc USC rate to 4.6pc, according to Mazars. This is the equivalent of a 1pc pay rise.

The limited impact of the proposal has been revealed while expectations run high following Taoiseach Enda Kenny's promise to phase out the tax and attract 70,000 emigrants home.

He recently indicated he plans to reduce the USC by €300m in the next Budget for low and middle-income workers.

The proposal to reduce the 5.5pc rate that affects more than half of households earning from €18,668 to €70,044 would cost the same amount.

It was put forward by the Tax Strategy Group this summer among options that include much smaller cuts in the tax, which was introduced at the height of the economic crisis.

"There is a risk that expectations are running high on abolishing the USC," he said. "Everyone is familiar with it and it's widely spoken about, but you might be expecting more than you'll receive."

Ibec director of policy Fergal O'Brien said cutting the marginal tax rate of 52pc, which includes income tax, PRSI and the USC, should be the "absolute priority".

He said this would target middle earners and attract workers to take up investment opportunities thrown up by Brexit.

A single worker has to be making only €33,800 - which is lower than average earnings - to be hit by the top rate of tax.

Ibec wants a €1,000 increase in the point at which workers hit the marginal rate and a clear road map to lower the rate to 45pc.

Mr O'Brien said the Government was doing a "three-card trick" by refusing to pay for an expensive indexation of tax credits. That had been standard practice by finance ministers in the past and would benefit workers.

He said it was using the money saved to spend on a USC cut, which gives it "more bang for its buck" politically, although it would spread the funds thinly as pensioners and landlords also pay the charge.

"The Government's biggest wheeze is that it wants to give the perception that it is cutting taxes, but is not delivering on what was standard practice of adjusting all the bands and credits in line with wage growth in the economy," he said.

"Workers are getting pay increases, but are not getting the same benefit as more of their wages are going on the top rate of tax. "Those on middle incomes need a break and deserve a break," he said.

"They are losing half their pay, and in some cases, more, which is still above a psychological threshold that they are working more for the Government than themselves."